The invention relates to a method and a device adapted for s, use in the placing of a suction anchor with an attached anchor chain or similar on the ocean bed, said suction anchor being lowered first without the anchor chain, and secured by suction to the ocean bed, after which the lower end of the anchor chain is lowered and connected to the suction anchor.
Suction anchors with associated anchor chains are used when floating installations of different kind are to be anchored to the ocean bed. Earlier it was common for the suction anchor and the associated anchor chain to be transported off shore and lowered to the ocean bed collectively. This resulted in very high costs since the suction anchor and the associated anchor chain have a great weight, often more than a thousand tons, and take up a lot of space, so that large surface vessels and heavy crane equipment were needed. The costs were reduced somewhat through the gradual change to transporting and lowering of the suction anchor and anchor chain separately. This involves reduced costs with respect to the surface vessel and crane equipment, but it has turned out that the reduction is balanced, to a large extent, by new costs that did not accrue when the suction anchor and the anchor chain were transported and lowered collectively. Of such costs may be mentioned that it will be necessary to provide a submarine vehicle with the equipment necessary for the connection of the suction anchor and the anchor chain on the ocean bed, that a far more complex device must be provided for connecting the suction anchor and the anchor. chain than when the connection is carried out before the lowering, that the work takes more time, etc. Another important drawback is that the known devices for connecting the suction anchor and the anchor chain on the ocean bed, are highly complicated constructions that give rise to many faults and delays during the connection.
The main object of the present invention is to provide a method and a device of the above type, wherein the suction anchor and the anchor chain are lowered to the ocean bed separately, and wherein the connecting of the suction anchor and the anchor chain can be carried out without the use of an expensive submarine vehicle performing the actual connecting. Other objectives are that the connecting is to take place without any use, worth mentioning, of mechanically movable parts or closing mechanisms, that the connecting shall be carried out without faults and by means of gravity, and in as few operations and otherwise with as few pieces of expensive utility equipment as possible.
As appears from the characterizing part of the present independent claim concerning the above method, this is realized by connecting the suction anchor and the lower end of the anchor chain in the following steps:
i) the lower end of the anchor chain is lowered into a vertically extending guiding element with a lower locking element arranged thereto, the guiding and locking elements being provided externally on the side wall of the suction anchor and formed with a bore each, arranged so that the longitudinal axes form an acute angle between themselves, and the lower end of the anchor chain has a preferably rod-like connecting element arranged thereto;
ii) the upper end of the connecting element is pulled outwards from the suction anchor, so that the connecting element is brought into a position, in which the longitudinal axis of the connecting element is concentric with the longitudinal axis of the bore of the locking element; and
iii) the connecting element is pulled outwards from the suction anchor in the direction along the longitudinal axis of the bore of the locking element until the lower end of the connecting element engages the locking element of the suction anchor, the lower end of the connecting element being formed as a locking piece with a cross-sectional shape adapted to the bore of the locking element.
As appears from the characterizing part of the present independent claim concerning the above device, through the connection of the suction anchor and the anchor chain, by means of a vertically extending guiding element provided with a lower locking element and a preferably rod-like connecting element, the connecting element being adapted for insertion into the guiding and locking elements and engagement with the locking element; through the provision of the guiding and locking elements externally on the side wall of the suction anchor, and their configuration with a bore each, arranged so that the longitudinal axes form an acute angle between themselves, and through the positioning of the connecting element on the lower end of the anchor chain and its configuration with a lower locking piece, the locking piece being of a cross-sectional shape adapted to the cross-sectional shape of the bore of the locking element. Other advantageous features of the invention appear from the present dependent claims and otherwise from the specification.